Conventionally, for example, Patent Document 1 describes an air conditioner that includes a refrigeration cycle capable of switching between an air-cooling operation and an air-heating operation. In the related art, such a refrigeration cycle includes a compressor, a first heat exchanger, a second heat exchanger, a third heat exchanger, a first expansion device, and a second expansion device.
The first heat exchanger is disposed in an air conditioning duct and has its air ventilation volume adjusted by a damper. The second heat exchanger is disposed on an upstream side with respect to the first heat exchanger within the air conditioning duct. The third heat exchanger is disposed outside the air conditioning duct.
These devices form a loop by connecting the compressor, the first heat exchanger, the first expansion device, the third heat exchanger, a first on/off valve, the second expansion device, and the second heat exchanger in this order with respect to the flow of a refrigerant.
A refrigerant passage, which is opened or closed by a second on/off valve, is provided between the inflow and outflow sides of the first expansion device. Another refrigerant passage, which is opened or closed by a third on/off valve, is provided between the outflow side of the first heat exchanger and the inflow side of the second expansion device. A further refrigerant passage, which is opened or closed by a fourth on/off valve, is provided between the outflow side of the third heat exchanger and the suction side of the compressor.
During the air-cooling operation, the first on/off valve and the second on/off valve are opened, the third on/off valve and the fourth on/off valve are closed, and the damper is set to a position where the air ventilation volume in the first heat exchanger is eliminated. Thus, the refrigerant discharged from the compressor passes through the first heat exchanger without dissipating any heat in the first heat exchanger, then passes through the first on/off valve, and subsequently dissipates heat in the third heat exchanger. Thereafter, the refrigerant is decompressed in the second expansion valve and then absorbs heat in the second heat exchanger. In this case, the air fed from the upstream side within the air conditioning duct is cooled down when passing through the second heat exchanger and then supplied to a space to be temperature-controlled while bypassing the first heat exchanger.
During the air-heating operation, the fourth on/off valve is opened, the first on/off valve, the second on/off valve, and the third on/off valve are closed, and the damper is set to a position where the air ventilation volume in the first heat exchanger is maximized. Thus, the refrigerant discharged from the compressor dissipates heat in the first heat exchanger and is then decompressed in the first expansion device. Subsequently, the refrigerant absorbs heat in the third heat exchanger and is returned to the compressor without passing through the second heat exchanger. In this case, the air fed from the upstream side within the air conditioning duct does not exchange any heat in the second heat exchanger and is heated when passing through the first heat exchanger to be supplied to the space to be temperature-controlled.